Background/objective: Although dietary supplement use has increased significantly among the general population, the interplay between vitamin D supplementation and other factors that influence vitamin D status remains unclear. The objective of this study was to identify predictor variables of vitamin D status in free-living subjects to determine the extent to which vitamin D supplements and other factors influence vitamin D status.
Subjects/methods: This was a retrospective, cross-sectional study involving 743 volunteers. Serum 25-hydroxy-vitamin D (25(OH)D) level and the variables diet, supplement usage, latitude of residence, ethnicity, age and body mass index (BMI) were used to predict vitamin D status in a summer and winter cohort.
Results: Supplemental vitamin D3 consumption was the most significant positive predictor, whereas BMI was the most significant negative predictor, of vitamin D status in each cohort. Other positive predictors were fortified beverage and dairy consumption in the summer and winter cohort, respectively. Negative predictors were: African American, Asian and Hispanic race in the summer; latitude of residence >36°N, Asian and Hispanic ethnicity in the winter. Mean(± s.d.) 25(OH)D levels were 101.1 (± 42.1) and 92.6 (± 39.0) nmol/l in summer and winter, respectively. Comparing non-supplement vs supplement users, approximately 38 vs 2.5% in the winter and 18 vs 1.4% in the summer had vitamin D levels <50 nmol/l.
Conclusions: Vitamin D supplementation was the most significant positive predictor of vitamin D status. Collectively, these data point to the practicality of utilizing vitamin D supplements to reduce hypovitaminosis D in adults throughout the United States.